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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "induction_var_range.h"
#include <limits>
namespace art {
/** Returns true if 64-bit constant fits in 32-bit constant. */
static bool CanLongValueFitIntoInt(int64_t c) {
return std::numeric_limits<int32_t>::min() <= c && c <= std::numeric_limits<int32_t>::max();
}
/** Returns true if 32-bit addition can be done safely. */
static bool IsSafeAdd(int32_t c1, int32_t c2) {
return CanLongValueFitIntoInt(static_cast<int64_t>(c1) + static_cast<int64_t>(c2));
}
/** Returns true if 32-bit subtraction can be done safely. */
static bool IsSafeSub(int32_t c1, int32_t c2) {
return CanLongValueFitIntoInt(static_cast<int64_t>(c1) - static_cast<int64_t>(c2));
}
/** Returns true if 32-bit multiplication can be done safely. */
static bool IsSafeMul(int32_t c1, int32_t c2) {
return CanLongValueFitIntoInt(static_cast<int64_t>(c1) * static_cast<int64_t>(c2));
}
/** Returns true if 32-bit division can be done safely. */
static bool IsSafeDiv(int32_t c1, int32_t c2) {
return c2 != 0 && CanLongValueFitIntoInt(static_cast<int64_t>(c1) / static_cast<int64_t>(c2));
}
/** Returns true for 32/64-bit integral constant. */
static bool IsIntAndGet(HInstruction* instruction, int32_t* value) {
if (instruction->IsIntConstant()) {
*value = instruction->AsIntConstant()->GetValue();
return true;
} else if (instruction->IsLongConstant()) {
const int64_t c = instruction->AsLongConstant()->GetValue();
if (CanLongValueFitIntoInt(c)) {
*value = static_cast<int32_t>(c);
return true;
}
}
return false;
}
/**
* An upper bound a * (length / a) + b, where a > 0, can be conservatively rewritten as length + b
* because length >= 0 is true. This makes it more likely the bound is useful to clients.
*/
static InductionVarRange::Value SimplifyMax(InductionVarRange::Value v) {
int32_t value;
if (v.a_constant > 1 &&
v.instruction->IsDiv() &&
v.instruction->InputAt(0)->IsArrayLength() &&
IsIntAndGet(v.instruction->InputAt(1), &value) && v.a_constant == value) {
return InductionVarRange::Value(v.instruction->InputAt(0), 1, v.b_constant);
}
return v;
}
/** Helper method to insert an instruction. */
static HInstruction* Insert(HBasicBlock* block, HInstruction* instruction) {
DCHECK(block != nullptr);
DCHECK(block->GetLastInstruction() != nullptr) << block->GetBlockId();
DCHECK(instruction != nullptr);
block->InsertInstructionBefore(instruction, block->GetLastInstruction());
return instruction;
}
//
// Public class methods.
//
InductionVarRange::InductionVarRange(HInductionVarAnalysis* induction_analysis)
: induction_analysis_(induction_analysis) {
DCHECK(induction_analysis != nullptr);
}
void InductionVarRange::GetInductionRange(HInstruction* context,
HInstruction* instruction,
/*out*/Value* min_val,
/*out*/Value* max_val,
/*out*/bool* needs_finite_test) {
HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop
if (loop != nullptr) {
// Set up loop information.
HBasicBlock* header = loop->GetHeader();
bool in_body = context->GetBlock() != header;
HInductionVarAnalysis::InductionInfo* info =
induction_analysis_->LookupInfo(loop, instruction);
HInductionVarAnalysis::InductionInfo* trip =
induction_analysis_->LookupInfo(loop, header->GetLastInstruction());
// Find range.
*min_val = GetVal(info, trip, in_body, /* is_min */ true);
*max_val = SimplifyMax(GetVal(info, trip, in_body, /* is_min */ false));
*needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip);
} else {
// No loop to analyze.
*min_val = Value();
*max_val = Value();
*needs_finite_test = false;
}
}
bool InductionVarRange::RefineOuter(/*in-out*/Value* min_val, /*in-out*/Value* max_val) {
Value v1 = RefineOuter(*min_val, /* is_min */ true);
Value v2 = RefineOuter(*max_val, /* is_min */ false);
if (v1.instruction != min_val->instruction || v2.instruction != max_val->instruction) {
*min_val = v1;
*max_val = v2;
return true;
}
return false;
}
bool InductionVarRange::CanGenerateCode(HInstruction* context,
HInstruction* instruction,
/*out*/bool* needs_finite_test,
/*out*/bool* needs_taken_test) {
return GenerateCode(context,
instruction,
nullptr, nullptr, nullptr, nullptr, nullptr, // nothing generated yet
needs_finite_test,
needs_taken_test);
}
void InductionVarRange::GenerateRangeCode(HInstruction* context,
HInstruction* instruction,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** lower,
/*out*/HInstruction** upper) {
bool b1, b2; // unused
if (!GenerateCode(context, instruction, graph, block, lower, upper, nullptr, &b1, &b2)) {
LOG(FATAL) << "Failed precondition: GenerateCode()";
}
}
void InductionVarRange::GenerateTakenTest(HInstruction* context,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** taken_test) {
bool b1, b2; // unused
if (!GenerateCode(context, context, graph, block, nullptr, nullptr, taken_test, &b1, &b2)) {
LOG(FATAL) << "Failed precondition: GenerateCode()";
}
}
//
// Private class methods.
//
bool InductionVarRange::NeedsTripCount(HInductionVarAnalysis::InductionInfo* info) {
if (info != nullptr) {
if (info->induction_class == HInductionVarAnalysis::kLinear) {
return true;
} else if (info->induction_class == HInductionVarAnalysis::kWrapAround) {
return NeedsTripCount(info->op_b);
}
}
return false;
}
bool InductionVarRange::IsBodyTripCount(HInductionVarAnalysis::InductionInfo* trip) {
if (trip != nullptr) {
if (trip->induction_class == HInductionVarAnalysis::kInvariant) {
return trip->operation == HInductionVarAnalysis::kTripCountInBody ||
trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe;
}
}
return false;
}
bool InductionVarRange::IsUnsafeTripCount(HInductionVarAnalysis::InductionInfo* trip) {
if (trip != nullptr) {
if (trip->induction_class == HInductionVarAnalysis::kInvariant) {
return trip->operation == HInductionVarAnalysis::kTripCountInBodyUnsafe ||
trip->operation == HInductionVarAnalysis::kTripCountInLoopUnsafe;
}
}
return false;
}
InductionVarRange::Value InductionVarRange::GetFetch(HInstruction* instruction,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) {
// Detect constants and chase the fetch a bit deeper into the HIR tree, so that it becomes
// more likely range analysis will compare the same instructions as terminal nodes.
int32_t value;
if (IsIntAndGet(instruction, &value)) {
return Value(value);
} else if (instruction->IsAdd()) {
if (IsIntAndGet(instruction->InputAt(0), &value)) {
return AddValue(Value(value), GetFetch(instruction->InputAt(1), trip, in_body, is_min));
} else if (IsIntAndGet(instruction->InputAt(1), &value)) {
return AddValue(GetFetch(instruction->InputAt(0), trip, in_body, is_min), Value(value));
}
} else if (instruction->IsArrayLength() && instruction->InputAt(0)->IsNewArray()) {
return GetFetch(instruction->InputAt(0)->InputAt(0), trip, in_body, is_min);
} else if (is_min) {
// Special case for finding minimum: minimum of trip-count in loop-body is 1.
if (trip != nullptr && in_body && instruction == trip->op_a->fetch) {
return Value(1);
}
}
return Value(instruction, 1, 0);
}
InductionVarRange::Value InductionVarRange::GetVal(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) {
if (info != nullptr) {
switch (info->induction_class) {
case HInductionVarAnalysis::kInvariant:
// Invariants.
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
return AddValue(GetVal(info->op_a, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, is_min));
case HInductionVarAnalysis::kSub: // second reversed!
return SubValue(GetVal(info->op_a, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, !is_min));
case HInductionVarAnalysis::kNeg: // second reversed!
return SubValue(Value(0),
GetVal(info->op_b, trip, in_body, !is_min));
case HInductionVarAnalysis::kMul:
return GetMul(info->op_a, info->op_b, trip, in_body, is_min);
case HInductionVarAnalysis::kDiv:
return GetDiv(info->op_a, info->op_b, trip, in_body, is_min);
case HInductionVarAnalysis::kFetch:
return GetFetch(info->fetch, trip, in_body, is_min);
case HInductionVarAnalysis::kTripCountInLoop:
case HInductionVarAnalysis::kTripCountInLoopUnsafe:
if (!in_body && !is_min) { // one extra!
return GetVal(info->op_a, trip, in_body, is_min);
}
FALLTHROUGH_INTENDED;
case HInductionVarAnalysis::kTripCountInBody:
case HInductionVarAnalysis::kTripCountInBodyUnsafe:
if (is_min) {
return Value(0);
} else if (in_body) {
return SubValue(GetVal(info->op_a, trip, in_body, is_min), Value(1));
}
break;
default:
break;
}
break;
case HInductionVarAnalysis::kLinear:
// Linear induction a * i + b, for normalized 0 <= i < TC.
return AddValue(GetMul(info->op_a, trip, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, is_min));
case HInductionVarAnalysis::kWrapAround:
case HInductionVarAnalysis::kPeriodic:
// Merge values in the wrap-around/periodic.
return MergeVal(GetVal(info->op_a, trip, in_body, is_min),
GetVal(info->op_b, trip, in_body, is_min), is_min);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetMul(HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) {
Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true);
Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false);
Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true);
Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false);
if (v1_min.is_known && v1_min.a_constant == 0 && v1_min.b_constant >= 0) {
// Positive range vs. positive or negative range.
if (v2_min.is_known && v2_min.a_constant == 0 && v2_min.b_constant >= 0) {
return is_min ? MulValue(v1_min, v2_min)
: MulValue(v1_max, v2_max);
} else if (v2_max.is_known && v2_max.a_constant == 0 && v2_max.b_constant <= 0) {
return is_min ? MulValue(v1_max, v2_min)
: MulValue(v1_min, v2_max);
}
} else if (v1_min.is_known && v1_min.a_constant == 0 && v1_min.b_constant <= 0) {
// Negative range vs. positive or negative range.
if (v2_min.is_known && v2_min.a_constant == 0 && v2_min.b_constant >= 0) {
return is_min ? MulValue(v1_min, v2_max)
: MulValue(v1_max, v2_min);
} else if (v2_max.is_known && v2_max.a_constant == 0 && v2_max.b_constant <= 0) {
return is_min ? MulValue(v1_max, v2_max)
: MulValue(v1_min, v2_min);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::GetDiv(HInductionVarAnalysis::InductionInfo* info1,
HInductionVarAnalysis::InductionInfo* info2,
HInductionVarAnalysis::InductionInfo* trip,
bool in_body,
bool is_min) {
Value v1_min = GetVal(info1, trip, in_body, /* is_min */ true);
Value v1_max = GetVal(info1, trip, in_body, /* is_min */ false);
Value v2_min = GetVal(info2, trip, in_body, /* is_min */ true);
Value v2_max = GetVal(info2, trip, in_body, /* is_min */ false);
if (v1_min.is_known && v1_min.a_constant == 0 && v1_min.b_constant >= 0) {
// Positive range vs. positive or negative range.
if (v2_min.is_known && v2_min.a_constant == 0 && v2_min.b_constant >= 0) {
return is_min ? DivValue(v1_min, v2_max)
: DivValue(v1_max, v2_min);
} else if (v2_max.is_known && v2_max.a_constant == 0 && v2_max.b_constant <= 0) {
return is_min ? DivValue(v1_max, v2_max)
: DivValue(v1_min, v2_min);
}
} else if (v1_min.is_known && v1_min.a_constant == 0 && v1_min.b_constant <= 0) {
// Negative range vs. positive or negative range.
if (v2_min.is_known && v2_min.a_constant == 0 && v2_min.b_constant >= 0) {
return is_min ? DivValue(v1_min, v2_min)
: DivValue(v1_max, v2_max);
} else if (v2_max.is_known && v2_max.a_constant == 0 && v2_max.b_constant <= 0) {
return is_min ? DivValue(v1_max, v2_min)
: DivValue(v1_min, v2_max);
}
}
return Value();
}
bool InductionVarRange::GetConstant(HInductionVarAnalysis::InductionInfo* info, int32_t *value) {
Value v_min = GetVal(info, nullptr, false, /* is_min */ true);
Value v_max = GetVal(info, nullptr, false, /* is_min */ false);
if (v_min.is_known && v_max.is_known) {
if (v_min.a_constant == 0 && v_max.a_constant == 0 && v_min.b_constant == v_max.b_constant) {
*value = v_min.b_constant;
return true;
}
}
return false;
}
InductionVarRange::Value InductionVarRange::AddValue(Value v1, Value v2) {
if (v1.is_known && v2.is_known && IsSafeAdd(v1.b_constant, v2.b_constant)) {
const int32_t b = v1.b_constant + v2.b_constant;
if (v1.a_constant == 0) {
return Value(v2.instruction, v2.a_constant, b);
} else if (v2.a_constant == 0) {
return Value(v1.instruction, v1.a_constant, b);
} else if (v1.instruction == v2.instruction && IsSafeAdd(v1.a_constant, v2.a_constant)) {
return Value(v1.instruction, v1.a_constant + v2.a_constant, b);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::SubValue(Value v1, Value v2) {
if (v1.is_known && v2.is_known && IsSafeSub(v1.b_constant, v2.b_constant)) {
const int32_t b = v1.b_constant - v2.b_constant;
if (v1.a_constant == 0 && IsSafeSub(0, v2.a_constant)) {
return Value(v2.instruction, -v2.a_constant, b);
} else if (v2.a_constant == 0) {
return Value(v1.instruction, v1.a_constant, b);
} else if (v1.instruction == v2.instruction && IsSafeSub(v1.a_constant, v2.a_constant)) {
return Value(v1.instruction, v1.a_constant - v2.a_constant, b);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::MulValue(Value v1, Value v2) {
if (v1.is_known && v2.is_known) {
if (v1.a_constant == 0) {
if (IsSafeMul(v1.b_constant, v2.a_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) {
return Value(v2.instruction, v1.b_constant * v2.a_constant, v1.b_constant * v2.b_constant);
}
} else if (v2.a_constant == 0) {
if (IsSafeMul(v1.a_constant, v2.b_constant) && IsSafeMul(v1.b_constant, v2.b_constant)) {
return Value(v1.instruction, v1.a_constant * v2.b_constant, v1.b_constant * v2.b_constant);
}
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::DivValue(Value v1, Value v2) {
if (v1.is_known && v2.is_known && v1.a_constant == 0 && v2.a_constant == 0) {
if (IsSafeDiv(v1.b_constant, v2.b_constant)) {
return Value(v1.b_constant / v2.b_constant);
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::MergeVal(Value v1, Value v2, bool is_min) {
if (v1.is_known && v2.is_known) {
if (v1.instruction == v2.instruction && v1.a_constant == v2.a_constant) {
return Value(v1.instruction, v1.a_constant,
is_min ? std::min(v1.b_constant, v2.b_constant)
: std::max(v1.b_constant, v2.b_constant));
}
}
return Value();
}
InductionVarRange::Value InductionVarRange::RefineOuter(Value v, bool is_min) {
if (v.instruction != nullptr) {
HLoopInformation* loop =
v.instruction->GetBlock()->GetLoopInformation(); // closest enveloping loop
if (loop != nullptr) {
// Set up loop information.
bool in_body = true; // use is always in body of outer loop
HInductionVarAnalysis::InductionInfo* info =
induction_analysis_->LookupInfo(loop, v.instruction);
HInductionVarAnalysis::InductionInfo* trip =
induction_analysis_->LookupInfo(loop, loop->GetHeader()->GetLastInstruction());
// Try to refine "a x instruction + b" with outer loop range information on instruction.
return AddValue(MulValue(Value(v.a_constant), GetVal(info, trip, in_body, is_min)),
Value(v.b_constant));
}
}
return v;
}
bool InductionVarRange::GenerateCode(HInstruction* context,
HInstruction* instruction,
HGraph* graph,
HBasicBlock* block,
/*out*/HInstruction** lower,
/*out*/HInstruction** upper,
/*out*/HInstruction** taken_test,
/*out*/bool* needs_finite_test,
/*out*/bool* needs_taken_test) {
HLoopInformation* loop = context->GetBlock()->GetLoopInformation(); // closest enveloping loop
if (loop != nullptr) {
// Set up loop information.
HBasicBlock* header = loop->GetHeader();
bool in_body = context->GetBlock() != header;
HInductionVarAnalysis::InductionInfo* info =
induction_analysis_->LookupInfo(loop, instruction);
if (info == nullptr) {
return false; // nothing to analyze
}
HInductionVarAnalysis::InductionInfo* trip =
induction_analysis_->LookupInfo(loop, header->GetLastInstruction());
// Determine what tests are needed. A finite test is needed if the evaluation code uses the
// trip-count and the loop maybe unsafe (because in such cases, the index could "overshoot"
// the computed range). A taken test is needed for any unknown trip-count, even if evaluation
// code does not use the trip-count explicitly (since there could be an implicit relation
// between e.g. an invariant subscript and a not-taken condition).
*needs_finite_test = NeedsTripCount(info) && IsUnsafeTripCount(trip);
*needs_taken_test = IsBodyTripCount(trip);
// Code generation for taken test: generate the code when requested or otherwise analyze
// if code generation is feasible when taken test is needed.
if (taken_test != nullptr) {
return GenerateCode(
trip->op_b, nullptr, graph, block, taken_test, in_body, /* is_min */ false);
} else if (*needs_taken_test) {
if (!GenerateCode(
trip->op_b, nullptr, nullptr, nullptr, nullptr, in_body, /* is_min */ false)) {
return false;
}
}
// Code generation for lower and upper.
return
// Success on lower if invariant (not set), or code can be generated.
((info->induction_class == HInductionVarAnalysis::kInvariant) ||
GenerateCode(info, trip, graph, block, lower, in_body, /* is_min */ true)) &&
// And success on upper.
GenerateCode(info, trip, graph, block, upper, in_body, /* is_min */ false);
}
return false;
}
bool InductionVarRange::GenerateCode(HInductionVarAnalysis::InductionInfo* info,
HInductionVarAnalysis::InductionInfo* trip,
HGraph* graph, // when set, code is generated
HBasicBlock* block,
/*out*/HInstruction** result,
bool in_body,
bool is_min) {
if (info != nullptr) {
// Handle current operation.
Primitive::Type type = Primitive::kPrimInt;
HInstruction* opa = nullptr;
HInstruction* opb = nullptr;
switch (info->induction_class) {
case HInductionVarAnalysis::kInvariant:
// Invariants.
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
case HInductionVarAnalysis::kLT:
case HInductionVarAnalysis::kLE:
case HInductionVarAnalysis::kGT:
case HInductionVarAnalysis::kGE:
if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) &&
GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) {
if (graph != nullptr) {
HInstruction* operation = nullptr;
switch (info->operation) {
case HInductionVarAnalysis::kAdd:
operation = new (graph->GetArena()) HAdd(type, opa, opb); break;
case HInductionVarAnalysis::kLT:
operation = new (graph->GetArena()) HLessThan(opa, opb); break;
case HInductionVarAnalysis::kLE:
operation = new (graph->GetArena()) HLessThanOrEqual(opa, opb); break;
case HInductionVarAnalysis::kGT:
operation = new (graph->GetArena()) HGreaterThan(opa, opb); break;
case HInductionVarAnalysis::kGE:
operation = new (graph->GetArena()) HGreaterThanOrEqual(opa, opb); break;
default:
LOG(FATAL) << "unknown operation";
}
*result = Insert(block, operation);
}
return true;
}
break;
case HInductionVarAnalysis::kSub: // second reversed!
if (GenerateCode(info->op_a, trip, graph, block, &opa, in_body, is_min) &&
GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) {
if (graph != nullptr) {
*result = Insert(block, new (graph->GetArena()) HSub(type, opa, opb));
}
return true;
}
break;
case HInductionVarAnalysis::kNeg: // reversed!
if (GenerateCode(info->op_b, trip, graph, block, &opb, in_body, !is_min)) {
if (graph != nullptr) {
*result = Insert(block, new (graph->GetArena()) HNeg(type, opb));
}
return true;
}
break;
case HInductionVarAnalysis::kFetch:
if (info->fetch->GetType() == type) {
if (graph != nullptr) {
*result = info->fetch; // already in HIR
}
return true;
}
break;
case HInductionVarAnalysis::kTripCountInLoop:
case HInductionVarAnalysis::kTripCountInLoopUnsafe:
if (!in_body && !is_min) { // one extra!
return GenerateCode(info->op_a, trip, graph, block, result, in_body, is_min);
}
FALLTHROUGH_INTENDED;
case HInductionVarAnalysis::kTripCountInBody:
case HInductionVarAnalysis::kTripCountInBodyUnsafe:
if (is_min) {
if (graph != nullptr) {
*result = graph->GetIntConstant(0);
}
return true;
} else if (in_body) {
if (GenerateCode(info->op_a, trip, graph, block, &opb, in_body, is_min)) {
if (graph != nullptr) {
*result = Insert(block,
new (graph->GetArena())
HSub(type, opb, graph->GetIntConstant(1)));
}
return true;
}
}
break;
default:
break;
}
break;
case HInductionVarAnalysis::kLinear: {
// Linear induction a * i + b, for normalized 0 <= i < TC. Restrict to unit stride only
// to avoid arithmetic wrap-around situations that are hard to guard against.
int32_t stride_value = 0;
if (GetConstant(info->op_a, &stride_value)) {
if (stride_value == 1 || stride_value == -1) {
const bool is_min_a = stride_value == 1 ? is_min : !is_min;
if (GenerateCode(trip, trip, graph, block, &opa, in_body, is_min_a) &&
GenerateCode(info->op_b, trip, graph, block, &opb, in_body, is_min)) {
if (graph != nullptr) {
HInstruction* oper;
if (stride_value == 1) {
oper = new (graph->GetArena()) HAdd(type, opa, opb);
} else {
oper = new (graph->GetArena()) HSub(type, opb, opa);
}
*result = Insert(block, oper);
}
return true;
}
}
}
break;
}
case HInductionVarAnalysis::kWrapAround:
case HInductionVarAnalysis::kPeriodic: {
// Wrap-around and periodic inductions are restricted to constants only, so that extreme
// values are easy to test at runtime without complications of arithmetic wrap-around.
Value extreme = GetVal(info, trip, in_body, is_min);
if (extreme.is_known && extreme.a_constant == 0) {
if (graph != nullptr) {
*result = graph->GetIntConstant(extreme.b_constant);
}
return true;
}
break;
}
default:
break;
}
}
return false;
}
} // namespace art